This invention relates generally to electrical power transfer and, more particularly, to automatic transfer switches.
An automatic transfer switch provides a continuous source of power for critical loads by automatically transferring from a normal power source to an emergency power source when the normal power source falls below a preset limit. Automatic transfer switches are in widespread use in hospitals, military installations, industrial sites, and commercial buildings where even brief power interruptions can be costly. Automatic transfer switches are also common to the power industry. Typical automatic transfer switches include a plurality of mechanical switching components controlled to minimize any interruptions during switching operations. Control of the switching components occurs through a series of sensing relays, transformers, and actuators, such as solenoids or linear motors to facilitate timely transfer from normal to emergency power. The solenoid actuators are energized until the controller senses that the switching component has moved to its desired position. Typically, a plurality of limit switches are positioned to provide a signal to the controller that switching is complete. Proper alignment of the limit switches facilitates a longer lasting automatic transfer switch because when the solenoid is energized, but the limit switch fails to actuate because of misalignment, the solenoid will be energized for a prolonged period of time which may damage the solenoid. Additionally, the limit switches, typically, are adjusted during assembly and/or installation resulting in an expenditure of time and raising assembly and/or installation costs.
Accordingly, it would be desirable to provide a cost-effective automatic transfer switch that is easy to assemble and install and facilitates a proper alignment of the limit switches and the switching components without adjustment during assembly and installation.
An automatic transfer switch includes a main body having a solenoid side and an auxiliary side. A solenoid side limit switch assembly is mounted to the solenoid side and an auxiliary side limit switch assembly is mounted on the auxiliary side. The solenoid side limit switch assembly includes a plurality of limit switches and a solenoid side mounting plate. The auxiliary side limit switch assembly includes a plurality of limit switches and an auxiliary side mounting plate. A unitary arc chute cover plate covers a plurality of phase plates.
The limit switches are in fixed relationship to the mounting plates and assembly time is decreased because the limit switches are not adjusted during assembly. Additionally the unitary construction of the arc chute cover plate facilitates a reduction in assembly time versus an automatic transfer switch having a plurality of separate cover plates. The automatic transfer switch facilitates a decrease in assembly time by utilizing a pre-assembled auxiliary limit switch assembly, a pre-assembled solenoid side limit switch assembly, and a unitary construction. The limit switches are not adjusted during assembly and installation providing for easy assembly and installation. Additionally, a tabbed mounting plate provides for easy mounting of the automatic transfer switch to an enclosure facilitating a decrease in installation time. Accordingly, an easy to assemble and install automatic transfer switch that is cost-effective is provided.